Out of This World – Two Neutron Stars Walk Into a Bar

Just on the heels of celebrating the Laser Interferometer Gravitational-Wave Observatory (LIGO) with a Nobel Peace Prize to some of its contributors, LIGO has led to another ground breaking event in history. On August 17, 2017, LIGO detected gravitational waves. Two seconds later, NASA’s Fermi Gamma-ray Space Telescope captured a gamma ray burst. All eyes turned to the location of the pulse, hoping to catch a glimpse.

This animation shows an artistic representation of the collision of two neutron stars. When they collide, they release a jet of gamma-rays followed by a kilonovae. (Credits: NASA’s Goddard Space Flight Center/CI Lab)

The source of the gravitational wave was the collision of two neutron stars. Neutron stars are what remains after a star explodes into a supernovae. Neutron stars are relatively small, about the size of a big city, but their mass is another story. These two neutron star in particular probably have a mass 10 to 60 percent greater than our Sun.

Hubble turned its eye to Galaxy 4993 to capture anything it could see after the detection of gravitational waves. It captured the kilonovae flare and watched as the emissions dissipated over the following 6 days. (Credits: NASA, ESA; acknowledgment: A. Levan (U. Warwick), N. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI))

What started as a slight tug toward each other as their gravities brought them together, turned into a death spiral. Eventually, they were circling each other a hundred times per minute, making the gravitational waves picked up by LIGO. Their collision created the gamma-ray burst and a kilonovae. It is believed that the material thrown from these merging objects, creating a jet of debris and a burst of gamma-rays, is the source of our Universe’s heavy metals, like gold and platinum. They are born from the crushing pressure inside neutron stars as particles are eventually released and reformed during the collision.

Capturing gravitational waves, followed closely by the detection from satellites like Hubble, Swift and Chandra as well as ground-based observatories is an incredible feat. Researchers recorded the death cycle of two massive objects 130 million light-years from Earth. Scientists will be pouring over this data for years, learning more about neutron stars and their emissions during the event of their collision.